(The New York Times News Service) -- Cell phones may be hazardous to your health.

For years, the question of whether cell phones pose a public health threat has been controversial. The cell phone industry and some American public health agencies say there is no definitive health risk. However, many researchers say enough evidence exists to warn Americans of possible harm.

Recently, the topic has gotten more attention in the United States and internationally.

A study released in August stated cell phone radiation changes DNA and causes cancer. Earlier this year, Finland joined several nations that have issued safety advisories on cell phone use. And this week, researchers from around the world met to discuss the issue at a Senate hearing and at the International Expert Conference on Cell Phones and Health in Washington.

Some researchers aren't concerned about any risk.

"There is more smoke than fire here," said Dr. Michael Thun, vice president emeritus of epidemiology and surveillance research for the American Cancer Society. "The radio frequency that comes from a cell phone is half way between a microwave oven and an FM radio. It's non-ionizing radiation, which doesn't change DNA and lead to cancer, and there has been no increase in brain cancer."

Other researchers believe America can't afford to wait to see if a problem exists.

"If you agree that cell phones cause brain tumors, then there will be a pandemic of brain tumors," said researcher Lloyd Morgan , chief author of the study "Cell Phones and Brain Tumors -- 15 Reasons for Concern," released in August, and director of the Central Brain Tumor Registry of the United States in Hinsdale, Ill.

"It's only a question of how large it will be, and when it will happen."

Cell phone use pervasive

An estimated 4 billion people in the world use cell phones, including more than 250 million Americans. According to Scarborough Research, a market research firm in New York City that tracks telecommunications data, about 2.8 million Metro Detroiters own cell phones.

Cell phones communicate via electromagnetic waves, a non-ionizing radiation. At issue is whether this type of radiation causes cancer or other health problems, such as damage to protective brain tissue.

In the last two years, a growing body of international research indicates that prolonged exposure to cell phone radiation may lead to brain tumors, mouth cancer and, for men, decreased fertility and testicular cancer for those who carry cell phones in their pockets.

A report released last week by the Environmental Working Group, an advocacy lobbyist agency in Washington, on cell phone radiation, cancer risks and children's health noted children have higher risks of developing brain tumors from cell phone use.

A 2008 multinational study spearheaded by the International Agency for Research on Cancer in France found that people who had used cell phones for more than 10 years had significantly increased risk of developing a brain tumor on the side of the head they favored for cell phone talks.

Earlier this year, Swedish researchers found the highest risk of brain tumors among people who started using cell phones during adolescence. And multiple studies reported young children's brains absorb more radiation than adults, making them more susceptible to brain tumors.

Some scientists disagree with these findings because cell phone technology has only existed for about 20 years and brain tumors can take 10 to 20 years to develop. Other criticisms of recent studies include flawed research methods and insufficient research time frames. And other experts say specific research on children has been too limited.

"I can't tell you for sure that cell phones are dangerous, but I can tell you that other governments have taken actions to warn people about the dangers and to take simple precautions," said Devra Lee Davis, an organizer of this week's Washington meeting and a professor of epidemiology at the University of Pittsburgh Graduate School of Public Health. The United Kingdom, Sweden, France, Israel, Germany and Finland have issued warnings to citizens about a potential link between cell phone radiation and brain tumors, and damage to the blood-brain barrier.

Those countries also have warned parents to limit children's cell phone use because of their softer skulls and developing brains. If the health risks concerning children are legitimate, Greg Alvarado of Dearborn Heights said he hopes the U.S. government also will issue an advisory.

"I have a 4-year-old daughter and she uses the cell phone every day," said Alvarado, 26.

Experts downplay risk

While cell phone models from some manufacturers, like the Nokia 1100, Apple iPhone, Motorola V195 GSM and BlackBerry 8300, include warnings in some instruction manuals to keep the phone away from the body, the cell phone industry claims there isn't cause for concern.

"The peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices do not pose a public risk," said John Walls, vice president of public affairs for the Cellular Telecommunications and Internet Association .

Dr. Larry Junck, professor of neurology at University of Michigan and head of the Brain Tumor Research Fund , also is doubtful about risks.

"We don't know a way in which cell phones can potentially cause brain tumors and that makes it less plausible there could be a relationship," he said. "With cell phones, the only kind of emission could be radio waves and the radio waves are more concentrated than radio waves are around us all the time, and we don't worry that those radio waves can cause brain tumors."

Dr. Sandeep Mittal said he believes the radiation poses no risk.

"There is no cause-and-effect," said Mittal, assistant professor in the Department of Neurosurgery at Wayne State University and co-leader of the Neuro-Oncology Multidisciplinary team at Karmanos Cancer Institute. "Just like microwave ovens, TV and radio, you are constantly exposed from even before you are born. Every child that is born starting from day one, they have had at least nine months of exposure through microwaves and radios.

Even if you don't have one, the waves are there."

In the research realm, a 2005 Danish study published in the American Academy of Neurology's journal examined people with and without brain tumors, and found no increased risk for brain tumors from cell phone use.

In 2000, based on a three-year study, the U.S. Food and Drug Administration, which tests drugs and medical devices for safety before use but does not traditionally test cell phones , said scientists had found no harmful health effects from wireless emissions. On its Web site, the FDA states: "The weight of scientific evidence has not linked cell phones with any health problems."

Nevertheless, a U.S. study on cell phone radiation is under way.

Christine Bruske Flowers, director of the National Institute of Environmental Health Sciences Office of Communications in Raleigh, N.C., said the FDA nominated the group's National Toxicology Program to begin a 10-year study on cell phone radiation in laboratory rats. Final results are expected in 2014.

Meanwhile, Morgan and other researchers suggest taking safety precautions such as using a wired earpiece or speaker phone, avoiding carrying the phone in pockets and keeping them at least a quarter-inch from the body in a holster.

"We're better safe than sorry," Morgan said. "If there is evidence that there might be a problem, and there is, and if there are no costs or low-cost things that we all can do, then those are things that should be done."

Copyright 2009 The New York Times News Service. All rights reserved.